Motors that provide rotational drilling motion include conventional drills and the Kumada piezo-motor, described in Sashida T., and T. Kenjo, An introduction to Ultrasonic Motors, Clarendon Press, Oxford (1993) pp. 13-16. This piezo-motor has been documented to have high efficient of 80%, relatively high torque density of 8.8 Nm/Kg, as described by Kumada A., “A piezoelectric motor,” Japanese J. of Applied Physics, Vol. 24, Supplement 24-2 (1985) pp. 739-741. In comparison, Maxon DC Brushless motors have an average efficiency of about 69% and torque density of about 0.2 Nm/Kg, as described in the May 2008 Maxon catalog at page 176.
One application of drills based on rotary motors is in extraterrestrial drilling such as that performed during U.S. and Soviet lunar drilling missions that took place in the early 1970s. In particular, astronauts who flew the Apollo 15, 16 and 17 missions successfully utilized a rotary percussive core drill, the so called Apollo Lunar Surface Drill or ALSD, designed and built by Martin Marietta, to penetrate up to 3.5 m below the surface. There are, however, a number of differences between the Apollo type drilling missions and future planetary missions including the presence of human operators during the Apollo missions and the available preload in the Soviet lunar drilling platforms.
There is a need for a drilling mechanism that can operate efficiently and reliably in the absence of human operators.